The invention relates to an optical switching arrangement and more particularly to a bistable switch with a laser as the light source, an electrooptical modulator formed as a first two-arm interferometer with control electrodes, and connected after the modulator, a second two-arm interferometer as a bistable element, the second interferometer having an output for a part of the light to which a photodiode is connected, the output voltage of which is used as a feedback magnitude for controlling the laser current.
In an optical switch of the type mentioned (DE-OS 38 18 865) it is possible to transform a continuously changing input signal into discrete output conditions in the form of light intensities or electrical voltages. The basis for this is a hysteresis curve which arises from the (G-u*) input/output characteristic, on which stationary values of the output intensities are achieved as a function of the proportionality factor, these values being used for the digitalisation. In the practical embodiment the output voltage is connected up to the electrodes of the two-arm interferometer used as a multi-stable element, so that the electrodes are then controlled up to the stationary value on the hysteresis curve, which corresponds to the light intensity fed in. The amplified voltage connected up to the electrodes of the multi-stable element as a control magnitude is then proportional to the light intensity and represents the measured value to be indicated for the intensity of the light fed to the multi-stable element.
In a further known arrangement (IEEE Journal of Quantum Electronics, Vol. QE-14, No. 8, August 1978, pages 577 to 580), which has an integrated optical 2.times.2 coupler, the light emanating from one of the two output arms is passed to a photo diode, the output voltage of which is passed back after amplification to the electrodes of the electrooptical modulator, which affects the phase mismatching of the two emanating light waves in the coupling area of the light coupler.
The advantage of these known arrangements lies in that the non-linearity required for the bistable mode is implemented by the transmission characteristics of the bistable element, and non-linear optical material, which requires relatively high optical input power, is not required.
The disadvantage of these known arrangements lies in that optoelectrical switches are required, i.e. switches in which an electrical feedback to the switch itself is necessary. The achievable switching speeds are therefore limited. More complex structures with a number of connected bistable electrooptical switches require optical as well as electrical connections through which the possibilities for implementation are drastically curtailed.